1. Field of the Invention
The invention relates to a dielectric antenna with an electromagnetic feed element and with a lens made of a dielectric material, the feed element emitting electromagnetic radiation and the lens in the feed region being supplied with electromagnetic radiation, the lens relaying the electromagnetic radiation and emitting it with the transmission region.
2. Description of Related Art
Dielectric antennas are known from various fields of engineering in quite varied types of construction. However, it is common to dielectric antennas that dielectric materials, especially those dielectric materials which have especially low losses, are used to guide and radiate electromagnetic waves. For example, using polytetraflouroethylene or polypropylene as the dielectric material or other dielectrics with low permittivity for the lens is known.
In industrial process engineering, dielectric antennas are often used, for example, for level measurement. In these and also other applications, it is especially advantageous if the antennas used have a direction of maximum radiation as narrow as possible, and at the same time, a type of construction as compact as possible. However, these requirements are contradictory with respect to the mechanical measures which must be conventionally taken for their technical implementation. A narrow directional characteristic in the direction of maximum radiation can be achieved only by a large aperture—i.e., opening area—of the transmission region of the lens, as is recognized. So that the aperture is also used for purposes of a narrow direction of maximum radiation, the electromagnetic radiation emitted from the transmission region of the lens must have a phase front as planar as possible, and this planar phase front can be implemented more easily with increasing length of the antenna; likewise, this opposes the desired compact type of construction.
Known dielectric antennas, in addition to difficult simultaneous implementation of a narrow direction of maximum radiation with a simultaneously compact type of construction, have a further disadvantage which is related to the mutual arrangement of the electromagnetic feed element and the lens made of dielectric material. For types of antenna construction in which the electromagnetic feed element and the lens are in direct contact with one another, the lens is surrounded at least by parts of the electromagnetic feed element, as a result of which the dielectric lens necessarily projects into the electromagnetic feed element and is exposed to electromagnetic radiation in the feed element (U.S. Pat. No. 6,023,246).
For other types of construction, the electromagnetic feed element and the lens made of dielectric material are arranged spaced apart from one another so that an intermediate space arises between the electromagnetic feed element and the dielectric lens.
The two aforementioned versions have the disadvantage that a type of construction which is also suitable, for example, for hygiene applications can only be poorly implemented. Aside from the implementation of an antenna with a lens which is at least partially encompassed by the feed element, which implementation is mechanically very demanding anyway, this type of construction also has the disadvantage that the transition from the feed element to the lens is in a region of the antenna that is shifted far forward and is comparatively exposed, and therefore, susceptible to dirt. In an antenna construction with intermediate spaces between the electromagnetic feed element and the lens, there is always the danger of fouling of those antenna surfaces which face the intermediate space; furthermore, overpressure and underpressure applications can be a problem as a result of the existing intermediate space.